Wait, Are Cavities Actually Contagious?

What did most of us do during the hard months of quarantine if not spend our days longing for life-after-lockdown? Well, #HotVaxxSummer is nearly half over, and many of us have been making up for time lost with our favorite activity: kissing. But how much do we actually know about the pros and cons of swapping spit? Are cavities contagious? And most importantly, should we add them to the long list of Cs we need to consider when choosing a kissing partner? (Common colds, COVID, cold sores … I could go on.)

For some Frenching enlightenment, I spoke with Tricia Quartley, DMD, a family dentist based in Brooklyn, New York and an ambassador for the American Dental Association (ADA), who says, “the bacteria that cause cavities can absolutely be spread via kissing.” It turns out Streptococcus mutans is one of the main bacterial culprits that cause cavities—often the result of excessive sugary snacking or less-than-consistent dental hygiene. The bacteria reside on the tooth’s surface and inside saliva that can be passed from person to person during a kiss.

Trading Streptococcus mutans (and other cavity-causing bacteria) is more likely to occur during kisses where partners exchange excessive saliva, but it can occur in any scenario where saliva is being passed from one person to another. A small 2016 study published in the Indian Journal of Medical Research found that, between birth and 6-months, 30% of infants had Streptococcus mutans in their mouths. Researchers concluded that, in many cases, it was passed to infants by their mothers. There are certainly various ways saliva might transfer from parent to child—including, researchers found, using a spoon before placing it in a baby’s mouth.

Before you swear off kissing (and spoon-sharing) altogether, it’s important to note that the risk of getting a cavity is likely based on your response to the bacteria, Quartley says. For instance, cavity-causing bacteria is more potent in the saliva of people who have an active cavity at the time of the kiss or have a history of frequent cavities, Quartley says. This isn’t to say that if you kiss someone who has a cavity, you will definitely have an unpleasant surprise at your next dental cleaning. But, if you are similarly susceptible to that bacterium, you may find kissing a cavity-prone person prompts the onset of cavities in your own mouth.

So what should you do if you’re kissing a cavity-prone person? Proceed with compassion. Having cavities is not a moral failing or detraction from how good a person or partner someone is. Cavities are often the result of not brushing and flossing daily, but research suggests some people may be genetically predisposed to having cavities and, despite their efforts to engage in best dental practices, will have a cavity once in a while anyway.

The best defense against giving or receiving cavities during a kiss is taking your own oral hygiene seriously. Dr. Quartley recommends brushing twice a day with fluoride toothpaste (also known as “nature’s cavity fighter”) because it protects the enamel of your teeth from acids and bacteria that lead to tooth decay. It’s also imperative that you clean between your teeth once a day, whether that’s with floss or a water pick, to remove debris. Excessive buildup of food particles and debris along the gum line can eventually cause gum disease, and you probably don’t want those problems in your life. Quartley adds: “Encourage the partner to do the same, as well as taking care of any active cavities.”

But it’s not all bad news when it comes to kissing hygiene—there are some solid benefits to consider as well.  The same way kissing someone who is cavity-prone can introduce you to bacteria that cause cavities, smooching someone who is not cavity-prone can introduce your mouth to cavity-fighting bacteria. Kissing also increases salivary flow that sweeps through the mouth, picking up debris lodged in your gums and neutralizing harmful acids along the way.

According to Quartley, whether kissing is overwhelmingly good or bad for your teeth is a case-by-case situation. But not everything we love in life needs to be a net-positive for our hygiene. Just as our dogs track dirt into our living rooms and our kids bring all sorts of germs home from school, kissing comes with a slight hygienic risk and some amazing potential rewards. Regardless, you can rest assured knowing you have the lion’s share of control over your dental hygiene. If you’re already brushing and flossing regularly, you’re doing a great job fighting those cavities.

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